Note 4 - Stock-based Compensation (Details Textual)	3 Months Ended
Jul. 29, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 29.61
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	3,100
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price \| $ / shares	$ 14.77
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	380,995
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price \| $ / shares	$ 11.46
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2,810,014

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
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Number of options outstanding, including both vested and non-vested options.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Number of share options (or share units) exercised during the current period.

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